Significance This intent of this study is to provide non invasive methods to assess safety and survival of intracranial grafts of fibroblasts containing a gene for expression of nerve growth factor. Cell grafts are placed in aged rhesus macaques to assess potential beneficial effects on cholinergic function. This type of somatic gene therapy is directed towards potential treatment of Alzheimer's disease. Objectives The objectives of this study are to use both magnetic resonance imaging (MRI) and positron emission tomography (PET) to evaluate both structural and functional neuroanatomy in aged macaques. These tools can then be used to assess significant features of aging as well as beneficial effects of gene therapy. Previous results with PET have shown changes in metabolic glucose utilization that correlate both with age and cognitive performance in specific brain regions. Studies to develop specific cholinergic markers have not yet been successful. Results Imaging studies during the past year have focused on MRI anatomic studies in the oldest class of aged rhesus, animals over 27 years of age. Three females and four males have been imaged and volumetric studies are proceeding on these animals to establish baseline parameters prior to further gene therapy studies. Future Directions Future studies will focus on both MRI and PET to evaluate intracranial grafts of cells producing NGF. In addition, both technologies are being used to document spontaneous changes observed in aged animals, particularly those animals falling into the oldest class of animals associated with documented changes in memory and biological function such as menopause. KEY WORDS aging, MRI, PET, neuroanatomy FUNDING NIH Grant RR00169